Table 2.

Elemental surface composition (atomic %) and oxygen to carbon ratio in different samples.

Samples	O	C	S	N	O/C
Native	32.76	63.00	0.26	0.62	0.52
SNC	28.79	70.23	0.21	–	0.41
SNC-P0	28.69	73.56	0.28	–	0.39
SNC-P2	30.22	77.50	0.26	0.62	0.39
SNC-P4	27.61	78.89	0.21	–	0.35
SNC-P6	27.76	79.31	0.28	–	0.35
SNP	30.22	65.70	0.26	0.62	0.46
SNP-P0	29.95	69.66	0.21	–	0.43
SNP-P2	28.98	72.46	0.28	–	0.40
SNP-P4	30.57	76.43	0.21	–	0.40
SNP-P6	28.83	77.91	0.28	–	0.37